| Mirror Fusion Test Facility | |
|---|---|
 The mirror fusion test facility during construction in 1983, part of the Yin-Yang magnets can be observed in the background. | |
| Device type | Magnetic mirror |
| Location | Livermore, California, U.S. |
| Affiliation | Lawrence Livermore National Laboratory |
| History | |
| Date(s) of construction | 1977 – 1986 |
| Preceded by | 2XIIB |
| Related devices | Tandem Mirror Experiment (TMX) |
The Mirror Fusion Test Facility, or MFTF, was an experimental magnetic confinement fusion device built using the tandem magnetic mirror design. It was, by far, the largest, most powerful and most expensive mirror machine ever constructed. Due to budget cuts, it was mothballed the day after its construction was complete, and sat unused for a year before being formally cancelled. $372 million dollars were spent on the system during its lifetime.
MFTF was the ultimate development of a series of machines at Lawrence Livermore National Laboratory (LLNL) that trace their history back to the early 1950s. Over the years one problem after another had been addressed, leading to designs using "baseball" and "yin-yang" mirrors. By the late 1960s, it appeared possible to build stable mirrors. However, these changes had also lowered their economic performance, to the point where they appeared unattractive as power generators.
In 1968, the Soviets demonstrated their tokamak systems were outperforming all others by a factor of at least ten. The path to practical fusion appeared open, and in the US, in the mid-1970s, Robert Hirsch began plans to produce a prototype power plant. Having secured a massive budget increase, and desiring a second design in case the tokamak didn't pan out, a study of the alternative concepts suggested the best developed was the mirror. The original MFTF was essentially a very large yin-yang mirror, expected around 1982.
Hirsch's associate, Stephen O. Dean, asked for ideas that would improve the economics of the mirror. This led to the tandem mirror concept, and a redesign as MFTF-B, with the original mirror becoming one end of a much larger machine. To test the new concept, a smaller machine that could be rapidly built was constructed, Tandem Mirror Experiment, or TMX. Construction of MFTF and TMX began in 1977 and TMX began operations in 1979.
By the early 1980s, TMX was beginning to demonstrate serious problems that suggested MFTF-B would not work as predicted. This was occurring around the same time that Ronald Reagan declared that the energy crisis was over. In a series of sweeping budget cuts across the entire energy research field, MFTF had its operational budget cancelled, although its construction budget survived. Construction completed in 1986, and the facility sat unused for a year being scavenged for parts by other researchers until it was formally cancelled in 1987 and disassembled.